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From:   John Hubbard <jhubbard@nvidia.com>
To:     Andrew Morton <akpm@linux-foundation.org>
CC:     Jens Axboe <axboe@kernel.dk>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Christoph Hellwig <hch@infradead.org>,
        "Darrick J . Wong" <djwong@kernel.org>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna@kernel.org>, Jan Kara <jack@suse.cz>,
        David Hildenbrand <david@redhat.com>,
        Logan Gunthorpe <logang@deltatee.com>,
        <linux-block@vger.kernel.org>, <linux-fsdevel@vger.kernel.org>,
        <linux-xfs@vger.kernel.org>, <linux-nfs@vger.kernel.org>,
        <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>,
        John Hubbard <jhubbard@nvidia.com>
Subject: [PATCH v2 7/7] fuse: convert direct IO paths to use FOLL_PIN
Date:   Tue, 30 Aug 2022 21:18:43 -0700
Message-ID: <20220831041843.973026-8-jhubbard@nvidia.com>
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Convert the fuse filesystem to use pin_user_pages_fast() and
unpin_user_page(), instead of get_user_pages_fast() and put_page().

The user of pin_user_pages_fast() depends upon:

1) CONFIG_BLK_USE_PIN_USER_PAGES_FOR_DIO, and

2) User-space-backed pages or ITER_BVEC pages.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 fs/fuse/dev.c    | 11 +++++++++--
 fs/fuse/file.c   | 32 +++++++++++++++++++++-----------
 fs/fuse/fuse_i.h |  1 +
 3 files changed, 31 insertions(+), 13 deletions(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 51897427a534..5de98a7a45b1 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -675,7 +675,12 @@ static void fuse_copy_finish(struct fuse_copy_state *cs)
 			flush_dcache_page(cs->pg);
 			set_page_dirty_lock(cs->pg);
 		}
-		put_page(cs->pg);
+		if (!cs->pipebufs &&
+		    (user_backed_iter(cs->iter) || iov_iter_is_bvec(cs->iter)))
+			dio_w_unpin_user_page(cs->pg);
+
+		else
+			put_page(cs->pg);
 	}
 	cs->pg = NULL;
 }
@@ -730,7 +735,9 @@ static int fuse_copy_fill(struct fuse_copy_state *cs)
 		}
 	} else {
 		size_t off;
-		err = iov_iter_get_pages2(cs->iter, &page, PAGE_SIZE, 1, &off);
+
+		err = dio_w_iov_iter_pin_pages(cs->iter, &page, PAGE_SIZE, 1,
+					       &off);
 		if (err < 0)
 			return err;
 		BUG_ON(!err);
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 1a3afd469e3a..01da38928d0b 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -625,14 +625,19 @@ void fuse_read_args_fill(struct fuse_io_args *ia, struct file *file, loff_t pos,
 }
 
 static void fuse_release_user_pages(struct fuse_args_pages *ap,
-				    bool should_dirty)
+				    bool should_dirty, bool is_user_or_bvec)
 {
 	unsigned int i;
 
-	for (i = 0; i < ap->num_pages; i++) {
-		if (should_dirty)
-			set_page_dirty_lock(ap->pages[i]);
-		put_page(ap->pages[i]);
+	if (is_user_or_bvec) {
+		dio_w_unpin_user_pages_dirty_lock(ap->pages, ap->num_pages,
+						  should_dirty);
+	} else {
+		for (i = 0; i < ap->num_pages; i++) {
+			if (should_dirty)
+				set_page_dirty_lock(ap->pages[i]);
+			put_page(ap->pages[i]);
+		}
 	}
 }
 
@@ -733,7 +738,7 @@ static void fuse_aio_complete_req(struct fuse_mount *fm, struct fuse_args *args,
 	struct fuse_io_priv *io = ia->io;
 	ssize_t pos = -1;
 
-	fuse_release_user_pages(&ia->ap, io->should_dirty);
+	fuse_release_user_pages(&ia->ap, io->should_dirty, io->is_user_or_bvec);
 
 	if (err) {
 		/* Nothing */
@@ -1414,10 +1419,10 @@ static int fuse_get_user_pages(struct fuse_args_pages *ap, struct iov_iter *ii,
 	while (nbytes < *nbytesp && ap->num_pages < max_pages) {
 		unsigned npages;
 		size_t start;
-		ret = iov_iter_get_pages2(ii, &ap->pages[ap->num_pages],
-					*nbytesp - nbytes,
-					max_pages - ap->num_pages,
-					&start);
+		ret = dio_w_iov_iter_pin_pages(ii, &ap->pages[ap->num_pages],
+					       *nbytesp - nbytes,
+					       max_pages - ap->num_pages,
+					       &start);
 		if (ret < 0)
 			break;
 
@@ -1483,6 +1488,10 @@ ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
 		fl_owner_t owner = current->files;
 		size_t nbytes = min(count, nmax);
 
+		/* For use in fuse_release_user_pages(): */
+		io->is_user_or_bvec = user_backed_iter(iter) ||
+				      iov_iter_is_bvec(iter);
+
 		err = fuse_get_user_pages(&ia->ap, iter, &nbytes, write,
 					  max_pages);
 		if (err && !nbytes)
@@ -1498,7 +1507,8 @@ ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
 		}
 
 		if (!io->async || nres < 0) {
-			fuse_release_user_pages(&ia->ap, io->should_dirty);
+			fuse_release_user_pages(&ia->ap, io->should_dirty,
+						io->is_user_or_bvec);
 			fuse_io_free(ia);
 		}
 		ia = NULL;
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 488b460e046f..6ee7f72e29eb 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -290,6 +290,7 @@ struct fuse_io_priv {
 	struct kiocb *iocb;
 	struct completion *done;
 	bool blocking;
+	bool is_user_or_bvec;
 };
 
 #define FUSE_IO_PRIV_SYNC(i) \
-- 
2.37.2